Application of dipole modeling in localization of mesio-temporal epileptogenic focus.

Improved methods for noninvasive localization of an epileptic focus, modeled as an electrical dipole, are developed in this research. For the head geometrical model, a three-dimensional (3-D) electromagnetic tracking system is utilized to measure the exact positions of electrodes. A nonlinear optimization technique, the Levenberg-Marquardt method, is adopted for dipole localization. For the optimization algorithm to converge to correct solution, the singular value decomposition (SVD) technique is used to extract the dominant component of the EEG spike for initial estimation and dipole localization. The localization results of varied montages, including standard 10-20 electrodes and enhanced temporal electrodes, with or without invasive sphenoid electrodes, are compared. Our experimental results indicate that dipole localization with enhanced temporal electrodes can be used as an alternative for the invasive sphenoid electrodes to differentiate the epileptogenic foci of mesio-temporal area from temporal convexity.